The present invention relates to an otoscope.
DE 2 029 892 A discloses an otoscope having a head portion and a speculum portion adjoining the head portion with a through-hole extending through the head and speculum portions. At the proximal end of the head portion, i.e. at the end which during an ear examination faces towards the person performing the examination, the through-hole is closed by a lens arranged in a lens frame guided horizontally and perpendicularly to the central axis of the through-hole by means of a dovetail guide at the proximal end of the head portion. If it is necessary to introduce an instrument through the through-hole into a patient's ear, the lens frame with the lens is removed from the guide by a lateral sliding movement in order to enable introduction of an instrument through the through-hole from the proximal side into the distally located ear.
A different solution is disclosed in DE 2 203 357 A. In the otoscope known from this citation, the lens is supported in a lens frame arranged at the proximal end side of head portion and being pivotable about an axis which is parallel to the central axis of the through-hole. The lens frame may be pivoted from a viewing position, in which the lens is aligned with the through-hole, into a clearance position, in which the proximal end of the through-hole is cleared to enable an instrument to be introduced through the through-hole into the ear.
Thus the two known otoscopes described above have in common that the lens is arranged such that it closes the proximal end of the through-hole, which means that it is not arranged inside the through-hole.
DE 20 2008 005 144 U1 discloses an otoscope comprising a speculum receptacle surrounding the through-hole at the distal end of the head portion, wherein a speculum made of plastic material may be attached to the speculum receptacle for being introduced into a patient's ear during an examination. After the examination the plastic speculum is ejected and replaced by a new one in order to avoid cross contamination.
In known otoscopes with the above-mentioned configuration, i.e. having a lens which closes the proximal end of the through-hole, the magnification is normally not higher than three-fold. The magnification of magnifying glass lenses is defined by the reference seeing distance (the least distance of distinct vision) and the focal length of the magnifying glass lens. The highest magnification is located at the focal point of the magnifying glass lens. For otoscopes a reference seeing distance of about 250 mm is considered to be a value that enables a comfortable viewing experience. After attachment of a plastic speculum the overall installation length of an otoscope is normally about 65 mm. Together with a distance of 15 mm between the plane of examination and the speculum tip, the distance between the magnifying glass lens and the object being examined is about 80 mm. Use of a magnifying glass lens having a focal length of 85 mm in these geometries will result in a magnification of about 2.95 times. Thus the magnification of an otoscope is limited by the installation length of the device and the resulting possible focal length of the lens. If a higher magnification is to be realized (i.e. a lens with shorter focal length is to be used), the range of sharp focus will be located nearer to the lens. Merely using a different lens in a given otoscope design would move the range of sharp focus into the attached speculum, which would render a sharp representation of the object to be examined impossible.
The object underlying the invention is to create an otoscope by means of simple design which enables to view the area to be examined in a patient's ear with high magnifications and excellent sharpness.